The present invention is directed to a method for avoiding etch-critical problem regions, particularly in the manufacture of silk screening plates, solder stop masks or interconnects on an interconnect base plate.
Before interconnects can be fashioned on an interconnect base plate with etching techniques or silk screening plates can be produced, plastic coatings as well as photosensitive coatings or copper coatings are stripped from a coated base plate in many etching procedures. Respective films that, for example, reproduce an interconnect course in a plane of a multi-layer printed circuit board or writing on a base plate form the basis for the etch-oriented procedures. The film is either physically present or in the form of an electronic description. The electronic description, for example an interconnect course in a plane of a layout, is present in the form of either elementary configuration elements or graphic elements. These configuration elements are respectively based on a describable basic geometric form and are digitally stored.
When etching off a full panoply of coatings from a coated base plate, large particles from the coatings to be stripped can be released due to under-etching in critical regions. Differing from the fabrication intent in the critical regions, the coating to be etched off is not removed over its entire height by etching procedures. Rather, the material of the coating is merely under-etched.
This is accompanied by the disadvantage that the etched-off material particles float within the etchant bath and deposit at different locations on the base plate. These deposits can, for example, lead to serious errors in the interconnect production.
The critical regions tend to form given tight interconnect guidance or interconnect elements that lie in extremely close proximity next to one another. Another critical region can, for example, be caused in that long geometric base forms lie at an acute angle relative to one another. Particular in this latter example, under-etching tends to occur.
In order to avoid under-etching in the critical regions, the surface images of the film were visually examined for such weak points. The weak points that were recognized were then eliminated by manual re-working of the critical regions.